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Posted (edited)

That looks to be broadly 450 RHA, which is about what I thought it is. This is highly significant if true, because it means what I supposed L26 and L27 are might be true also. Hmm, good news. Or at least, better than Ive been assured it was.

 

 

Thanks for that. Im not remotely technically minded to comment on how good this is, how does it compare to american 105mm rounds of the same period?

 

well if round penetrate 435(path of round inside angled target) at 2km, i think at vertical plate it will penetrate less than 435(long rod penetrate more at angled targets)

vtTxVR0rf_s.jpg

 

it's interesting to find more about L23A1 vs 150mm/60 ect, but no info for now...

 

compare to 105mm, i don't know how much M774 can penetrate, but L23A1 better than M735 and M111 imho

Edited by Wiedzmin
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Posted

This is a very odd table. Just looking at the penetration at 0 km when firing the round from a new gun at +34°C...

A 490 mm penetration path would require a 130 mm steel plate to be sloped at 75° (at 74° the line of sight is only 471)! So did they actually use a 130 mm plate sloped at 75° or am I misunderstanding the table? Because according to Lanz-Odermatt, the penetration values of APFSDS ammunition against 75° slope are about ~35% larger than against 0° slope.

Posted

What document is this from?

120mm Report for Preliminary Acceptance Annex J pp 1-6

 

This is a very odd table. Just looking at the penetration at 0 km when firing the round from a new gun at +34°C...

A 490 mm penetration path would require a 130 mm steel plate to be sloped at 75° (at 74° the line of sight is only 471)! So did they actually use a 130 mm plate sloped at 75° or am I misunderstanding the table? Because according to Lanz-Odermatt, the penetration values of APFSDS ammunition against 75° slope are about ~35% larger than against 0° slope.

yes it's very strange test, and seem to be 75°, + don't know right term in english heading angle(?) +- 13-16°(left and right), but it used to imitate T-72 glacis, so it must be in 68-70° range.

 

but if i find more "standard" penetration test i will post it

  • 2 months later...
Posted (edited)

RB2HGGiYrCs.jpg

 

L23A1 core Tungsten-Nickel-Copper (W.Ni.Cu - S.T.A) overall shot length 510mm

 

Total Weight 7,89kg

Sub-Projectile Total Weight 3.89kg

Penetrator

Material S.T.A.

Weight 3.69 kg

Length 410 mm

Diameter 29.0 mm

L/D Ratio 14.1 : 1

Muzzle Velocity - (From Lll Gun using L8A1 Charge)

 

Velocity Drop (m/s/1000 m) 55

 

 

New Gun

-33C- 1494 m/s

+21C 1549 m/s

+52C 1587 m/s

 

 

! So did they actually use a 130 mm plate sloped at 75° or am I misunderstanding the table?

don't know about 130 at this moment, but for 150mm, yes, it's have 71 and 74,8 ° (when testing BD26)

Edited by Wiedzmin
Posted

...

In 1976 UK tried new APFSDS and L11 combo which has shown the best performance in terms of armour penetration. Hence US gave UK more time to develop the new 120 mm gun - EXP-M13A.

....

 

Missed this the first time but the designation should be the EXP19-M13A.

The ordnance development work was to enable the gun system to match the mounting and C-of-G configuration / limitations required to suit the XM1.

  • 6 months later...
Posted

Found out what that penetration table for L23A1 is supposed to mean. The numbers have nothing to do with a 130mm plate. The key is that the penetration numbers are all for a semi-infinite plate at a 68 degree obliquity and it's just the LOS penetration depth. The T-72M hull has 400mm RHA equivalent of effective armour in relative LOS thickness, so the requirement was to ensure that L23A1 can defeat the T-72M hull at 3.5 km. I calculated the penetration for all 5 ranges at +21°C using the velocities given in the table and dimensions given by Wiedzmin and they all came out exactly like the results in the firing table. Average error was just 0.0027%. It was only a matter of rounding up or rounding down.

  • 4 weeks later...
Posted (edited)

I had assumed the "130mm single RHA target" simply refers to the NATO "single medium": 130mm RHA sloped at 60 degrees (not 68)... and then they put a few RHA blocks behind that to calculate semi-infinite penetration.

 

Can you post more of this doc Wiedzmin? Maybe there's some additional text that explains the oddity.

Edited by Olds
  • 4 weeks later...
Posted (edited)

they simply change angle of inclination for 130mm plate to reach required IOS

Edited by Wiedzmin
Posted

It's not new, it's from the same document, they make same thing with 150mm plate for bd26 and later rounds, so for not inclined plates there will be much smaller numbers of penetration(test were done only on plates inclined up to 71-75 degrees) and if take to account that 427mm for L23A1 it's path of round inside inclined target but not it's penetration...

Posted

That's very weird. You can't determine penetration depth by simulating semi-infinite plate by just increasing the angle. The data you get from testing the same plate at different angles will be different for the same impact velocity.

Posted

China does the same. They have one target plate (220 mm) for their 105 mm, 120 mm and 125 mm APFSDS rounds - they just change the slope for different rounds.

  • 2 weeks later...
Posted

That's very weird. You can't determine penetration depth by simulating semi-infinite plate by just increasing the angle. The data you get from testing the same plate at different angles will be different for the same impact velocity.

If it is 'it's path of round inside inclined target' then that is going to not be especially inaccurate. The lower efficiency of angled plate vs APFSDS at non deflecting angles is mostly from a shorter channel due to dig in, so it will not show upward biased results if you measure the channel length, as it will if you use the LOS @ 90 deg.

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